44mm Piston Dimentional Data Wanted - Stihl + Husky

[Brewz]

also, how do you mount your 026 jugs to machine the squish?
Mine has some long fins that will make it difficult to bolt to a plate.

Do you grind these off ?

 

[drf256]

I like 105/120/78

 

[drf256]

I use a mandrel for squish. I need to change that.

Randy has a thread somewhere. You put a spacer on the area that's stamped "A" on your jug. Then you bolt it to a square plate through the cylinder bolt holes at the base. So long bolts.

You need to square it parallel to the Chuck by loosening and tightening those nuts.

Once square, you use the 4 jaw independent Chuck to center the chamber. Rinse and so repeat till perfect.

 

[Brewz]

Thanks mate
I am going to build a plate for it.

@Mastermind do you have a picture of how to do the spacer properly.

I have also ordered a bit of 60mm nylon bar.

I will use this saw as the learning experience.
I might even look orotund for a cheap cylinder to try out before I go cutting up my nice OEM jug

 

[Brewz]

I made one





Now to track down some 5" long 5mm screws

 

[Brewz]

I'm going to redo my 024/6 soon. I will futz wth this Pistons geometry a bit.

I'm already at a base of .206 IIRC.

Dropping it another .040 ain't working on this saw.

Sorry Mate. I just don't see the same thing you do on this one.

I am gonna try to 700* aluminum braze the exhaust roof on an AM jug.

I dont think this is going to work for you with a jug that has already been cut.
I really needs to be done with a virgin jug.

I am really keen to see what an 026 will do with the timing you have on your saw but with lower compression
J's 660's performance with the improved timings and sub 200 psi really has my mind ticking over.

 

[drf256]

Looks great Brewz.

 

[Brewz]

I wonder if the fins would be strong enough to hold it to cut the squish and the base?

 

[drf256]

I wonder if the fins would be strong enough to hold it to cut the squish and the base?

I doubt it.

There's a reason that "those in the know" do things a certain way. It's not cause they want to spend more time doing it.

Every time I've tried to take a shortcut, it just cost me time and money.

I bought threaded rod to do mine. Make studs out of it. You can even tack weld the back to the plate and gring the spot if you ever need to replace the stud.

 

[Brewz]

Yeah I figured it was done the long way for a reason.
Its just difficult without a lathe when it comes to all the prep work of making a nylon mandrel for 1 saw.

I really need a lathe but am in a bit of a financial rut at the moment and cant afford one and all the tooling.

I plan to use threaded rod.
I have tapped the plate so I can put a lock nut on the back and hold it in nice and solid

 

[drf256]

I hope your experiment works.

Part of me really thinks you're gonna mount that 246 piston and find that your initial ex roof, without any machine work, is gonna come in at 85-90. Then your gonna do all that work and get right back at 95.

I hope I'm wrong. If you could ask the mods to move this to the regular "chainsaw" section, I bet you get more opinions.

I could ask, but it's your thread and therefore your choice.

 

[Brewz]

Happy for it to be moved mate

I am basing the theory of this experiment around the gains found when fitting a 288 piston in the 660
The same thing would happen in the 660 with a short top husky 288 piston..... exhaust roof would come in higher.

@jmssaws
Did you do any timing measurements on the 660 with the 288 piston before you cut it?

 

[drf256]

@Mastermind

Would this thread be appropriate to move to the regular "Chainsaw" section?

 

[drf256]

A lot going on here Brewz.

If it's a flat top with longer skirts, it is going to reduce crankcase volume a bit as well.

So you may be able to go with a numerically higher transfer.

 

[Brewz]

Im not going to stab in the dark any more till I get a piston, bolt it to a rod and start measuring

 

[Brewz]

Na, on second thought, leave it here.

I will start a new thread

 

[drf256]

Cool bud.

When do u think you'll be getting yours?

 

[Red97]

You could always cut windows in a 346 piston.

It is 1.2mm shorter compression height, and 3mm longer than the 44mm stihl according to the meteor website.

I imagine the 246 has similar specs being it has 2.5mm less stroke than the 346.

 

[Brewz]

Cool bud.

When do u think you'll be getting yours?

WAY after you

@Red97 I dont have the skill to start creating windows in pistons that will be doing 15000 + rpm. It would end in shrapnel and tears!

I have posted a new thread in the "chainsaw" forum area.

http://opeforum.com/threads/fitting-a-husqvarna-246-piston-to-a-stihl-026.1971/

hook in over there folks!

 

[Wonkydonkey]

I just wanted to bump this thread up. As I’m thinking along similar lines. But I also need to get my head around a few things.

I wanted to have a higher crown to wrist pin, to get more compression, I can cut the squish with an old piston, but I don’t want to get a belt sander to the base.

I will have a read of the other thread and the link that doc posted, as well as a reread of 2stroke tuners hand book, inperticular the crank rotation and position to port timings